Micro-arc oxidation process of magnesium alloy hub

Abstract

The invention discloses a micro-arc oxidation process of a magnesium alloy hub, which comprises the following steps of: immersing the magnesium alloy hub into electrolyte in a micro-arc oxidation tank, inputting sine alternating current with the same frequency into the micro-arc oxidation tank, continuing for a certain time, and then inputting alternating current with different frequencies or phases, in the electrolysis process, the temperature and the liquid level of the micro-arc oxidation tank are monitored in real time through a control system, and the cooling power is controlled according to the temperature of the micro-arc oxidation tank. According to different micro-arc requirements, voltage sources with different frequencies or phases can be input into the electrode bars, so that periodic signals with different duty ratios can be obtained by inputting sinusoidal quantities with different frequencies, better oxidation is realized, the surface hardness of the magnesium alloy hub is improved, the oxidation strength of partial areas such as screw holes is enhanced, and the service life of the magnesium alloy hub is prolonged. And the porcelainizing thickness is increased.

Description

Technical Field

[0001] The present invention relates to the micro-arc oxidation technology on the surface of magnesium alloy wheels, and particularly to a micro-arc oxidation process for magnesium alloy wheels. Background Art

[0002] The micro-arc oxidation process mainly relies on the matching adjustment of the electrolyte and electrical parameters. Under the action of the instantaneous high temperature and high pressure generated by arc discharge, a modified ceramic coating mainly composed of the matrix metal oxide and supplemented by the electrolyte components is grown on the surface of valve metals such as aluminum, magnesium, titanium and their alloys. Its anti-corrosion and wear resistance are significantly better than those of traditional anodic oxidation coatings, and its application on components has received wide attention. During the micro-arc oxidation process, chemical oxidation, electrochemical oxidation and plasma oxidation exist simultaneously, so the formation process of the ceramic layer is very complex.

[0003] At present, there are many problems in the micro-arc oxidation surface ceramization treatment. First of all, the micro-arc oxidation process consumes a large amount of energy per unit area during processing, which limits the area of the processed workpiece. At present, it is more for the micro-arc of small parts or the micro-arc treatment of flat plates, and there is no mature method for the surface treatment of large parts such as wheels. Secondly, due to the irregular influence of discharge parameters on the microstructure of the oxide film and the unclear mechanism of the influence of the electrolyte system on the micro-arc, the structural change of the micro-arc oxidation is affected by many factors. To obtain a better-quality oxide film, different electrical parameter requirements are needed in the initial, middle and late stages of the micro-arc oxidation film formation. By coordinating and adjusting the electrical parameters, the microstructure can be optimized. For example, by controlling the discharge sparks, a good surface roughness of the film layer can be obtained. Summary of the Invention

[0004] Aiming at the problems existing in the prior art, the present invention provides a micro-arc oxidation process for magnesium alloy wheels to improve the surface hardness of magnesium alloy wheels and enhance the performance of magnesium alloy wheels.

[0005] To achieve the above object, the specific scheme of the present invention is as follows:

[0006] A micro-arc oxidation process for magnesium alloy wheels, which immerses the magnesium alloy wheels in the electrolyte in the micro-arc oxidation tank, first inputs sinusoidal alternating current with the same frequency into the micro-arc oxidation tank, and then inputs alternating current with different frequencies or phases after a certain period of time. During the electrolysis process, the temperature and liquid level of the micro-arc oxidation tank are monitored in real time through a control system, and the cooling power is controlled according to the temperature of the micro-arc oxidation tank.

[0007] Preferably, the solute ratio of the electrolyte is: 15 parts of sodium silicate, 12 parts of sodium hydroxide, 15 parts of sodium fluoride, 11 parts of ammonium bifluoride, and 3012 parts of polyethylene glycol. When preparing the electrolyte, gas needs to be injected into it for rolling and stirring.

[0008] Preferably, the solvent of the electrolyte is ultrapure water, and the alternating current input to the micro-arc oxidation tank during the electrolysis process has a current of 5-8 A and a voltage of 300 V.

[0009] Preferably, when smooth surface treatment is required, an AC voltage source with the same frequency is used. When micro-arcs with a certain duty cycle are to be employed, according to Fourier series, a non-sinusoidal periodic signal can be decomposed into the superposition of sinusoidal quantities with different frequencies. The formula is as follows:

[0010]

[0011] where F is the Fourier transform symbol, ω is the frequency of the signal, f(t) represents the sinusoidal signal in the time domain, which can be voltage or current, and the integral with respect to time represents the transformation from the time domain to the frequency domain. The superposition of sinusoidal quantities with different frequencies yields a square-wave signal with different duty cycles.

[0012] Preferably, for areas where strengthening is required in fine details, the multi-beam energy field synthesis technology is adopted. By combining each beam at multiple points, a beam array is formed. Using different phase information, a synthetic micro-arc energy field is generated. The basic principle is to utilize the interference effect of energy waves. By adjusting the parameters between micro-arcs of different array units, the energy in some angles is enhanced while the energy in other angles becomes smaller. The beam array is the array pattern, which refers to the graph of the relative field strength of the field energy varying with direction at a certain distance:

[0013]

[0014] where M represents M beams, * represents conjugate, x i (t) is the input signal represented by a vector, specifically a current or voltage signal, and w(θ) represents the weighting coefficient of signals with different phases;

[0015] To form a main lobe in a certain direction θ, the composition of the weighting vector of the field energy former in the desired direction is:

[0016] w(θ) = [1, e jωτ , …, e j(M-1)ωt T

[0017] According to this weighting vector, if there is only one signal from the direction θ in space, the form of its direction vector a(θ) is the same as this weighting vector. Therefore, we obtain:

[0018] y(t) = w H (θ)x(t) = a H (θ)x(t)

[0019] ​Where, H represents the conjugate transpose. According to the above formula, the output power of a conventional beamformer can be expressed as:

[0020] P CBF (θ) = E{y(t) 2} = E{w H (θ)x(t)w H (θ)x(t)} =

[0021] E{w H (θ)x(t)x H (t)w(θ)} = w H (θ)Rw(θ) = a H (θ)Ra(θ)

[0022] Where, P CBF (θ) represents the average power synthesis in different directions. The matrix R is the covariance matrix of the array output x(t), that is, R = E{x(t)x H (t)};

[0023] According to different requirements, the maximum signal-to-noise ratio criterion and the minimum mean square error criterion are obtained by using the beamforming algorithm, so that the ratio of the power of the desired signal component to the power of the noise component is maximized, and the mean square error between the array output and a certain desired response is minimized.

[0024] Preferably, the micro-arc oxidation tank includes a tank body, a plurality of electrode rods distributed in the tank body, and a cooler connected to the outside of the tank body. The electrode rods are arranged in an array in the center and on the side walls of the tank body. The tank body includes an inner tank and an outer tank. There is an interlayer for accommodating cooling water between the inner tank and the outer tank. The cooler includes a circulation pump and a radiator, and the circulation pump is connected to the interlayer.

[0025] Preferably, the control system includes a main control unit and a storage unit, a detection unit, a cooler control unit, a power supply unit, a data transmission unit, and a display unit all connected thereto. An electric control cabinet is provided outside the micro-arc oxidation tank, and the control system is embedded in the electric control cabinet.

[0026] Preferably, the main control unit includes an MCU, a memory, a key, and a power supply. The MCU is connected to the electrode rods and inputs voltage sources with different frequencies or phases to each electrode rod respectively.

[0027] Preferably, the detection unit includes a temperature detection module, a pressure detection module, and a voltage and current detection module. The temperature detection module includes a temperature sensor, and the temperature sensor is arranged on the side wall of the tank body. The pressure detection module includes a liquid level sensor, and the liquid level sensor is arranged on the side wall of the tank body.

[0028] Preferably, the cooler control unit includes a cooler driving module, a radiator control module, and a circulation pump control module all connected thereto. The cooler driving module is used to drive the radiator control module and the circulation pump control module, and thus drive the radiator and the circulation pump. The cooler control unit controls the flow rate of the cooling water in the interlayer through the circulation pump, and cools the circulating cooling water through the radiator.

[0029] Preferably, the storage unit uses a large-capacity flash storage medium. The power supply unit includes a battery module, a charging module, and a power control module. The data transmission unit includes a data packaging module and a wireless transmission module. The display unit includes a display screen module, an interface module, and a display driving module for displaying the status and functions of the system.

[0030] Adopting the technical solution of the present invention has the following beneficial effects:

[0031] The present invention can input voltage sources with different frequencies or phases to each electrode rod according to different micro-arc requirements. In this way, by inputting sinusoidal quantities with different frequencies, periodic signals with different duty cycles can be obtained, achieving better oxidation, thereby improving the surface hardness of the magnesium alloy wheel hub, strengthening the oxidation intensity of partial areas such as screw holes, and increasing the porcelainization thickness. The present invention also adopts an electrolyte with a phosphorus-free formula, reducing environmental pollution and being more environmentally friendly.

[0032] The present invention also collects the temperature and pressure data of the micro-arc oxidation tank in real time through the detection unit, and uploads the information to the background cloud server by using the wireless transmission module. The large-capacity storage unit can record various data during the oxidation process and display them through the display unit. The main control unit realizes feedback and control according to the current voltage, current, temperature, pressure and other data, and finally can effectively control the oxidation process and the temperature, pressure, etc. of the electrolyte, achieving energy conservation, emission reduction and efficiency improvement. Description of the Drawings

[0033] Figure 1 is the flow chart of the present invention;

[0034] Figures 2 to 5 is the simulation diagram of the present invention;

[0035] Figure 6 is the three-dimensional structure diagram of the micro-arc oxidation tank of the present invention;

[0036] Figure 7 is the functional module block diagram of the control system of the present invention.

[0037] Among them, 1 - main control unit, 2 - storage unit, 3 - detection unit, 301 - temperature sensor, 302 - liquid level sensor, 4 - cooler control unit, 5 - power supply unit, 6 - data transmission unit, 7 - display unit, 8 - micro - arc oxidation tank, 801 - tank body, 802 - electrode rod, 803 - cooler, 804 - inner tank, 805 - outer tank, 806 - circulation pump, 807 - radiator, 9 - electrical control cabinet. Specific implementation mode

[0038] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0039] Refer to Figure 1 , the present invention provides a micro - arc oxidation process for magnesium alloy wheels. Immerse the magnesium alloy wheels in the electrolyte in the micro - arc oxidation tank. First, input sinusoidal alternating current with the same frequency into the micro - arc oxidation tank. After a certain period of time, input alternating current with different frequencies or phases. During the electrolysis process, the temperature and liquid level of the micro - arc oxidation tank are monitored in real time through the control system, and the cooling power is controlled according to the temperature of the micro - arc oxidation tank.

[0040] The solvent of the electrolyte is ultrapure water, and the ratio of solutes is: 15 parts of sodium silicate, 12 parts of sodium hydroxide, 15 parts of sodium fluoride, 11 parts of ammonium bifluoride, and 3012 parts of polyethylene glycol. When preparing the electrolyte, gas needs to be introduced for rolling and stirring, aiming to make the electrolyte mix evenly and cool down; during the electrolysis process, the current of the alternating current input into the micro - arc oxidation tank is 5 - 8A and the voltage is 300V.

[0041] When the wheels need smooth surface treatment, through an AC voltage source with the same frequency. When a certain duty - cycle micro - arc is required, according to Fourier series, a non - sinusoidal periodic signal can be decomposed into the superposition of sinusoidal quantities with different frequencies. The formula is as follows:

[0042]

[0043] Among them, F is the Fourier transform symbol, ω is the frequency of the signal, f(t) represents the sinusoidal signal in the time domain, which can be voltage or current. The integral with respect to time represents the transformation from the time domain to the frequency domain. The superposition of sinusoidal quantities with different frequencies results in a square - wave signal with different duty - cycles.

[0044] For areas that need to be strengthened, such as screw holes, the multi-beam energy field synthesis technology is adopted. By combining the beams of multiple points, a beam array is formed. Using different phase information, a synthetic micro-arc energy field is generated, forming a stronger energy field space on the local surface, strengthening the surface of the fine areas of the hub, enhancing the oxidation intensity of some areas (such as screw threads), increasing the porcelainization thickness, and hardening the strength. The multi-beam formation algorithm of the energy field combines the signals of multiple energy arc fields (usually arranged in a multi-phase control manner), suppresses the propagation of non-target direction field signals, and enhances the target direction signals; furthermore, it can achieve energy focusing in a specific direction, effectively improving the energy concentration and forming a better surface layer. The basic principle is to utilize the interference effect of energy waves. By adjusting the parameters between the micro-arcs of different array units, the energy in some angles is enhanced while the energy in other angles becomes smaller. The beam array is the array pattern, which refers to the graph of the relative field strength of the field energy changing with direction at a certain distance:

[0045]

[0046] Among them, M represents M beams, * represents conjugate, and x i (t) is the input signal represented by a vector, specifically a current or voltage signal, and w(θ) represents the weighting coefficient of signals with different phases;

[0047] To form a main lobe in a certain direction θ, the weighted vector of the field energy former in the desired direction is composed of:

[0048] w(θ) = [1, e jωt , …, e j(M-1)ωt T

[0049] According to this weighted vector, if there is only one signal from the direction θ in space, the form of its direction vector a(θ) is the same as this weight vector, so we get:

[0050] y(t) = w H (θ)x(t) = a H (θ)x(t)

[0051] Among them, H represents conjugate transpose. According to the above formula, the output power of the conventional beam former can be expressed as:

[0052] P CBF (θ) = E{y(t) 2} = E{w H (θ)x(t)w H (θ)x(t)} =

[0053] E{w H (θ)x(t)x H ​(t)w(θ)} = w H (θ)Rw(θ) = a H (θ)Ra(θ)

[0054] Among them, P CBF ( θ ) represents the average power synthesis in different directions. The matrix R is the covariance matrix of the array output x(t), that is, R = E { x(t)x H (t) } ;

[0055] According to different requirements, the maximum signal-to-noise ratio criterion and the minimum mean square error criterion are obtained by using the beamforming algorithm, so that the ratio of the power of the desired signal component to the power of the noise component is maximized, and the mean square error between the array output and a certain desired response is minimized. For the simulation results, see Figure 2 and Figure 3 ; For the array formed by the electrode rods, by adjusting the phase, the effect of energy superposition can be achieved. For the simulation results, see Figure 4 and Figure 5 .

[0056] Referring to Figure 6 , the micro-arc oxidation tank 8 includes a tank body 801, a plurality of electrode rods 802 distributed in the tank body 801, and a cooler 803 connected to the outside of the tank body 801. The electrode rods 802 are arranged in an array in the center and on the side walls of the tank body 801. The tank body 801 includes an inner tank 804 and an outer tank 805. There is an interlayer for accommodating cooling water between the inner tank 804 and the outer tank 805. The cooler 803 includes a circulation pump 806 and a radiator 807. The circulation pump 806 is connected to the interlayer; an electric control cabinet 9 is provided outside the micro-arc oxidation tank 8, and the control system is embedded in the electric control cabinet 9.

[0057] Referring to Figure 7 , it includes a main control unit 1 and a storage unit 2, a detection unit 3, a cooler control unit 4, a power supply unit 5, a data transmission unit 6, and a display unit 7 all connected to it. This system is connected to the micro-arc oxidation tank 8.

[0058] The main control unit 1 includes an MCU, a memory, a key, and a power supply. The MCU is connected to the electrode rods 802 and inputs voltage sources with different frequencies or phases to each electrode rod 802 respectively, and is used to receive the data of the detection unit 3.

[0059] The detection unit 3 includes a temperature detection module, a pressure detection module, and a voltage and current detection module. The temperature detection module includes a temperature sensor 301, which is disposed on the side wall of the tank 801 and is used to detect the temperature inside the tank 801. The pressure detection module includes a liquid level sensor 302, which is disposed on the side wall of the tank 801 and is used to detect the height of the electrolyte in the tank 801.

[0060] The cooler control unit 4 includes a cooler drive module, a radiator control module, and a circulation pump control module all connected thereto. The cooler drive module is used to drive the radiator control module and the circulation pump control module, and thus drive the radiator 807 and the circulation pump 806. The cooler control unit 4 controls the flow rate of the cooling water in the interlayer through the circulation pump 806, and cools the circulating cooling water through the radiator 807, thereby controlling the cooling temperature of the tank 801.

[0061] The storage unit 2 uses a large-capacity flash storage medium to store various types of data of each part of the system in the local storage space. The power supply unit 5 includes a battery module, a charging module, and a power control module to provide power for the system and ensure the normal operation of the device. The data transmission unit 6 includes a data packaging module and a wireless transmission module to achieve reliable data transmission. The wireless transmission module can transmit the data to the cloud server. The display unit 7 includes a display screen module, an interface module, and a display drive module to display the status and functions of the system.

[0062] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. Any equivalent structural transformation made by using the description and drawings of the present invention under the inventive concept of the present invention, or direct / indirect application in other related technical fields, is included in the protection scope of the present invention.

Claims

1. A micro-arc oxidation process for a magnesium alloy wheel hub, characterized in that: The magnesium alloy wheel hub is immersed in the electrolyte in the micro-arc oxidation tank. Sinusoidal alternating current of the same frequency is first input into the micro-arc oxidation tank, and then alternating current of different frequency or phase is input after a certain period of time. During the electrolysis process, the temperature and liquid level of the micro-arc oxidation tank are monitored in real time through the control system, and the cooling power is controlled according to the temperature of the micro-arc oxidation tank.

2. The micro-arc oxidation process for magnesium alloy wheel hub according to claim 1, characterized in that: The solvent of the electrolyte is ultrapure water, and the solute ratio of the electrolyte is: 15 parts of sodium silicate, 12 parts of sodium hydroxide, 15 parts of sodium fluoride, 11 parts of ammonium bifluoride, and 12 parts of polyethylene glycol 30. When preparing the electrolyte, gas needs to be injected into it for rolling stirring.

3. The micro-arc oxidation process for magnesium alloy wheel hub according to claim 2, characterized in that: During the electrolysis process, the alternating current input into the micro-arc oxidation tank has a current of 5-8A and a voltage of 300V.

4. The micro-arc oxidation process for magnesium alloy wheel hub according to claim 3, characterized in that: When smooth surface treatment is required, an AC voltage source with the same frequency is used. When a micro-arc with a certain duty cycle is required, according to the Fourier series, a non-sinusoidal periodic signal can be decomposed into a superposition of sinusoidal quantities of different frequencies. The formula is as follows: Where F is the Fourier transform symbol, ω is the frequency of the signal, f(t) represents a time domain sinusoidal signal, which can be a voltage or a current. The integral of time represents the transformation from the time domain to the frequency domain. The superposition of sinusoidal quantities of different frequencies results in square wave signals with different duty cycles.

5. The micro-arc oxidation process for magnesium alloy wheel hub according to claim 3, characterized in that: For the subtle areas that need to be strengthened, multi-beam energy field synthesis technology is used. The beams at multiple points are combined to form a beam array. Different phase information is used to generate a synthetic micro-arc energy field. The basic principle is to use the interference effect of energy waves and adjust the parameters between the micro-arcs of different array units to enhance the energy at some angles and reduce the energy at other angles. The beam array is an array pattern, which refers to a graph of the relative field strength of the field energy changing with direction at a certain distance: Where M represents M beams, * represents conjugation, and x i (t) is the input signal represented by a vector, specifically a current or voltage signal, and w(θ) represents the weighting coefficient of the signal with different phases; In order to form a main lobe in a certain direction θ, the weighting vector of the field energy former in the desired direction is constructed as follows: w(θ)[1,e jωτ ,...,e j(M-1)ωτ ] T According to this weighted vector, if there is only one signal from the direction θ in the space, its direction vector a(θ) has the same form as this weighted vector, so we get: y(t)=w H (θ)x(t)=a H (θ)x(t) Where H represents the conjugate transpose. According to the above formula, the output power of a conventional beamformer can be expressed as: P CBF (θ)=E{y(t) 2 }=E{w H (θ)x(t)w H (θ)x(t)}= E{w H (θ)x(t)x H (t)w(θ)}=w H (θ)Rw(θ)=a H (θ)Ra(θ) Among them, P CBF (θ) represents the average power synthesis in different directions, and the matrix R is the covariance matrix of the array output x(t), that is, R = E{x(t)x H (t)}; According to different requirements, the beamforming algorithm is used to obtain the maximum signal-to-noise ratio criterion and the minimum mean square error criterion, so that the ratio of the desired signal component power to the noise component power is maximized and the mean square error between the array output and a certain expected response is minimized.

6. The micro-arc oxidation process for a magnesium alloy wheel hub according to any one of claims 1 to 5, characterized in that: The micro-arc oxidation tank includes a tank body, a plurality of electrode rods distributed in the tank body, and a cooler connected to the outside of the tank body. The electrode rods are distributed in an array in the center and side walls of the tank body. The tank body includes an inner tank and an outer tank. There is an interlayer between the inner tank and the outer tank for accommodating cooling water. The cooler includes a circulating pump and a radiator. The circulating pump is connected to the interlayer.

7. The micro-arc oxidation process for magnesium alloy wheel hub according to claim 6, characterized in that: The control system includes a main control unit and a storage unit, a detection unit, a cooler control unit, a power supply unit, a data transmission unit, and a display unit all connected thereto. An electric control cabinet is provided outside the micro-arc oxidation tank, and the control system is embedded in the electric control cabinet.

8. The micro-arc oxidation process for magnesium alloy wheel hub according to claim 7, characterized in that: The main control unit includes an MCU, a memory, a button and a power supply. The MCU is connected to the electrode rods and inputs voltage sources of different frequencies or phases to each electrode rod.

9. The micro-arc oxidation process for magnesium alloy wheel hub according to claim 7, characterized in that: The detection unit includes a temperature detection module, a pressure detection module and a voltage and current detection module. The temperature detection module includes a temperature sensor, which is arranged on the side wall of the tank body. The pressure detection module includes a liquid level sensor, which is arranged on the side wall of the tank body.

10. The micro-arc oxidation process for magnesium alloy wheel hub according to claim 7, characterized in that: The cooler control unit includes a cooler driving module and a radiator control module and a circulating pump control module connected thereto. The cooler driving module is used to drive the radiator control module and the circulating pump control module, and then drive the radiator and the circulating pump. The cooler control unit controls the flow rate of cooling water in the interlayer through the circulating pump, and cools the circulating cooling water through the radiator. The storage unit uses a large-capacity flash storage medium. The power supply unit includes a battery module, a charging module and a power control module. The data transmission unit includes a data packaging module and a wireless transmission module. The display unit includes a display screen module, an interface module and a display driver module, which are used to display the status and function of the system.

Images